Noninvasive imaging in cardiac resynchronization therapy--part 1: selection of patients

Cardiac resynchronization therapy (CRT) is an established therapy for patients with advanced heart failure, depressed left ventricular function, and wide QRS complex. However, individual response varies, and a substantial amount of patients do not respond to CRT. Recent studies observed that assessment of inter- and particularly intraventricular dyssynchrony may allow identification of potential responders to CRT. In addition, presence of scar tissue and venous anatomy may play a role in the selection of candidates. In this review, an extensive overview of the available dyssynchrony measurements is provided using echocardiography as well as magnetic resonance imaging (MRI) and nuclear imaging. Furthermore, other information derived from MRI, nuclear imaging, and computed tomography useful for the selection of potential candidates for CRT will be discussed.